diff --git a/unions/unions.c b/unions/unions.c
new file mode 100644
index 0000000..9db9dc5
--- /dev/null
+++ b/unions/unions.c
@@ -0,0 +1,16 @@
+#include <stdint.h>
+
+typedef enum {
+    CMD_SET_LEVEL = 1,
+    CMD_SET_LIGHTS = 2,
+    CMD_SET_DIST = 3,
+} command_t;
+
+typedef struct Message {
+    uint8_t type;
+    union {
+        struct { uint8_t level; } set_level;
+        struct { uint8_t on; } set_lights;
+        struct { float distance; } set_distance;
+    } data;
+} Message;